This invention relates to optical interconnection apparatuses (optical circuit boards) for mutually connecting optical elements, components and/or devices used in optical communications or optical information processing, such as optical elements, optical circuit packages and optical circuit devices.
To permit interconnections between plural optical elements in an optical circuit package or optical interconnections between plural optical circuit packages or between optical circuit devices on each of which optical packages are mounted, these optical elements, optical circuit packages and optical circuit devices are generally provided at terminals thereof with optical connectors to interconnect them together via optical fibers. As these optical fibers have to be arranged with loose in this case, it is a current circumstance that, on an optical circuit package or inside and/or on a back side of an optical circuit devices, intricately routed lines of the optical fibers extend overlapping one another in the form of a bird""s nest and hence occupy a large space. For an optical interconnection process which requires a large space and considerable interconnecting labor due to such complex routing, a simple process has been proposed to solve these, problems by routing optical fibers on a two-dimensional planar surface as desired. As disclosed in JP 2,574,611 B, for example, an optical interconnection apparatus which uses a sheet or base with a pressure-sensitive adhesive coated thereon to hold optical fibers in place has been proposed.
Incidentally, the optical interconnection apparatus disclosed in JP 2,574,611 B is obtained in such a way that upon its fabrication, optical fibers are located by a pressure-sensitive adhesive on a base (base layer) or fiber jackets to form a routing pattern and the routing pattern is then covered with a material similar to a material used for the base, whereby a protective layer is formed. This process is however accompanied by problems in that as optical fibers so located increase in number and the optical fibers increase more overlapped portions (cross-over routing) in the routing pattern so formed, the resulting routing layer of the optical fibers becomes thicker and, because the tacky surface with which the optical fibers are in contact becomes smaller at the overlapped portions of the optical fibers, the protective layer cannot be arranged evenly. There is a further problem in that at the overlapped portions of the optical fibers in the routing pattern, the fixing force by the pressure-sensitive adhesive becomes weaker and the optical fibers are allowed to move, thereby resulting in displacements in the routing pattern (a loss in the intactness of the routing pattern). Moreover, general optical fibers range from 125 to 250 xcexcm in diameter so that at an overlapped area of three optical fibers, for example, the routing layer of the optical fibers becomes as thick as 375 to 750 xcexcm. An increase in the overlapped portions of optical fibers in a routing pattern develops lifted portions (air pockets) in a lower part of a protective layer around optical fibers, so that a problem arises in the reliability against temperatures and humidities and in addition, the optical circuit board becomes extremely weak to breakage which may be caused by deformation such as bending.
To solve these problems, it is studied to hold optical fibers, which are routed overlapping one another on an adhesive layer, in place by forming a protective resin layer over the optical fibers. In this case, however, combined use of a most commonly-employed acrylic pressure-sensitive adhesive as the adhesive layer and a silicone-base material, which is generally employed as a sealant in the field of semiconductors or the like, in the protective resin layer involves a problem in the adhesion with the acrylic pressure-sensitive adhesive material, which is a plastic material, because of good release properties of the silicone material, although this combined use is excellent in reliability, stress relaxation, heat resistance, freeze resistance, moisture resistance, chemical resistance, dust resistance and electrical insulation property owing to the characteristics of these materials. An optical circuit board so fabricated is therefore prone to breakage such as separation by deformation such as bending. As a result, insufficiency arises in holding optical fibers in place, resulting in development of a further problem in that the optical fibers undergo displacements in the routing pattern (a lose in the intactness of the routing pattern).
The present invention has been completed with a view to solving such problems in the conventional art. An object of the present invention is, therefore, to provide a novel optical interconnection apparatus, which can hold in place and protect routed optical fibers against external force (pulling, bending, scratching and the like), permits easy optical inter-connections without a loss in the intactness of a routing pattern of the optical fibers routed overlapping one another as described above, and is excellent in reliability such as environmental resistancexe2x80x94such as heat resistance and freeze resistancexe2x80x94and firm adhesion to a protective resin layer.
Each optical interconnection apparatus according to the present invention has plural optical fibers, which are routed in a two-dimensional plane and are provided at opposite ends thereof with end portions adapted to permit optical interconnections thereto, and at least one protective resin layer by which said optical fibers are held in place. In a first aspect, an optical interconnection apparatus is characterized in that the protective resin layer is formed from a silicone-base material curable through a condensation reaction with liberation of an oxime or liberation of an alcohol, is joined with a base or another protective resin layer via an adhesive layer, and the adhesive layer comprises an acrylic pressure-sensitive adhesive. In a second aspect, an optical interconnection apparatus is characterized in that the protective resin layer is formed from a silicone-base material curable by crosslinking through a hydrosilation reaction and an adhesive promoter, is joined with a base or another protective resin layer via an adhesive layer, and the adhesive layer comprises an acrylic pressure-sensitive adhesive. Further, in a third aspect, an optical interconnection apparatus is characterized in that the protective resin layer is formed of a silicone-base material, is joined with a base or another protective resin layer via an adhesive layer, and the adhesive layer comprises a silicone-base pressure-sensitive adhesive curable by crosslinking through a hydrosilation reaction.
In each of these optical interconnection apparatus according to the present invention, protective resin layers by which optical fibers are held in place, respectively, may be joined to opposite sides of the base via adhesive layers, respectively. As an alternative, another protective resin layer may be arranged on a back side of the base. As a further alternative, plural protective resin layers by which optical fibers are held in place, respectively, may be joined together via the adhesive layer.
In an optical interconnection apparatus according to a still further aspect, plural optical interconnection apparatuses as described above are joined together via an adhesive layer formed of a silicone-base pressure-sensitive adhesive, whereby a stacked structure is formed.